Table 1.

Demographic, clinical, dietary, and laboratory characteristics of adults enrolled in the NHANES III, based on the presence and stage of CKDa

CharacteristicNon-CKDCKDP
Stage 1Stage 2Stage 3Stage 4 or 5
Prevalence (%)86.26.23.53.80.2
Age (yr)41.1 ± 0.443.7 ± 0.859.5 ± 0.970.2 ± 0.870.7 ± 1.8<0.0001
Male gender (%)48.444.653.038.739.60.0070
Race/ethnicity (%)
    white76.064.880.986.866.7
    black10.617.510.77.523.1<0.0001
    Mexican American5.57.33.01.42.8
    other7.910.45.44.37.4
Serum creatinine (mg/dl)1.0 ± 0.01.0 ± 0.01.2 ± 0.01.5 ± 0.04.0 ± 0.4<0.0001
eGFR (ml/min per 1.73 m2)103.7 ± 0.6115.2 ± 1.076.8 ± 0.450.8 ± 0.321.1 ± 1.3<0.0001
Vitamin D levels (ng/ml; %)
    >3045.933.439.536.517.0
    15 to 3045.752.551.452.855.8<0.0001
    <158.414.19.110.727.2
Taking vitamin D supplements (%)27.923.225.627.117.10.0800
Total vitamin D intake (diet + supplements; IU/d)309.1 ± 7.3282.0 ± 13.4324.5 ± 22.3319.6 ± 19.2288.7 ± 57.90.3000
Current smokers (%)29.232.623.213.719.6<0.0001
Hypertension (%)17.633.359.372.774.4<0.0001
BMI (kg/m2)26.3 ± 0.127.2 ± 0.328.2 ± 0.527.7 ± 0.226.7 ± 1.1<0.0001
Diabetes (%)4.618.628.321.729.8<0.0001
Non-HDL cholesterol ≥160 (mg/dl, %38.742.957.468.450.2<0.0001
Serum CRP (mg/dl; %)
    undetectable74.160.658.750.835.1
    0.30 to 0.9919.824.127.030.837.4<0.0001
    ≥16.115.214.318.427.4
Serum albumin (g/dl)4.2 ± 0.04.2 ± 0.04.1 ± 0.04.0 ± 0.03.8 ± 0.1<0.0001
Corrected serum calcium (mg/dl)9.2 ± 0.09.3 ± 0.09.4 ± 0.19.5 ± 0.09.4 ± 0.1<0.0001
Serum phosphorus (mg/dl)3.5 ± 0.03.4 ± 0.03.4 ± 0.03.5 ± 0.04.1 ± 0.1<0.0001
No medical insurance (%)13.614.77.62.50.1<0.0001
Education <12 yr (%)19.727.932.843.849.4<0.0001
Income <200% of federal poverty level (%)32.642.036.845.955.1<0.0001
  • a BMI, body mass index; CKD, chronic kidney disease; CRP, C-reactive protein; eGFR, estimated GFR; NHANES III, Third National Health and Nutrition Examination Survey.